Applicant claims priority under 35 U.S.C. 119 for Application No. 7125/73 filed Feb. 14, 1973 in the Patent Office of Great Britain.
This invention concerns improvements in or relating to optical systems for measuring relative displacement or velocity and more particularly optical systems suitable for use as odometers or speedometers.
Background prior art is found in the following patents:
U.s. pat. Nos., 2,016,036, 2,413,349, 3,336,480, 3,511,569, 3,677,647. PA0 United Kingdom Patent Nos., 1,118,879, 1,123,950, 1,144,488, PA0 French Patent No. 2,143,950.